Abstract
The vertex arboricity va(G) of a graph G is the minimum number of colors the vertices can be colored so that each color class induces a forest. It was known that \(va(G)\le 3\) for every planar graph G. In this paper, we prove that \(va(G)\le 2\) if G is a planar graph without intersecting 5-cycles.

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This work is supported by NSFC (11271006, 11631014), XJEDU2016I046 and XJEDU2014S067 of China.
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Cai, H., Wu, J. & Sun, L. Vertex arboricity of planar graphs without intersecting 5-cycles. J Comb Optim 35, 365–372 (2018). https://doi.org/10.1007/s10878-017-0168-3
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DOI: https://doi.org/10.1007/s10878-017-0168-3